Air Conditioning is So Expensive!

by Chris Bjorklund

 Guest Expert Michael McCutcheon, owner of McCutcheon Construction, tells us about less costly ways to cool your house on hot days.

Air conditioning is still the best way to cool a building during hot weather, although in very dry climates, one can use evaporative coolers (“swamp coolers”) instead, which use the cooling effect of evaporating water. While they consume some water, they use less energy. They also don’t reduce humidity, and don’t work in humid climate zones since the evaporative effect is so much less in a humid atmosphere.

Presuming you’re in the mixed climate of the Bay Area and need Air Conditioning (as opposed to evaporative cooling), as with any energy device, the first thing to do to lower the cost is to reduce the load. In this case, just as with heat loss in winter, insulation and weather-stripping are key. Adding insulation to your attic will be a big help. Another suggestion is to use a light colored, reflective roof (a “cool” roof). This will reduce the amount of heat rays that penetrate into your home. Alternatively, you can install a radiant barrier, which is a reflective layer under your roof. This reflective layer bounces back the infrared rays to keep your attic and home cooler.

Another good idea is to install double pane windows with Low-E glass. This Low-E glass has a coating (a “low emissivity” coating), which reduces the passage of heat rays (infra-red) while allowing most of the visible light to pass through. If replacing the windows is too expensive, try having window coatings installed. Low-E films applied to the inside of your glass reflect a certain amount of the heat away. However, our experience is that double pane windows (combined with a well-sealed, insulating wood frame) with the Low-E glass are considerably more effective than applied films on single pane glass.

Again, just as with heating loss for winter, make sure your house is well sealed against air leakage. You can have your house tested for leaks by a Home Performance Contractor who will use a Blower Door to measure the amount of air leaking from your home. The less air leakage the better, and you can use sealants, caulking, weather-stripping, etc. to plug any leaks you may have.

Once you’ve done all the load reduction you can, it’s time to take a look at your AC unit. Ideally, it’s Energy Star labeled and is at least 14 SEER (Seasonal Energy Efficiency Ratio), which means you’ll use less electricity to run the unit. Make sure it’s been serviced recently, and ask the service provider what the efficiency rating is. If your unit isn’t up to snuff, consider upgrading to a more efficient one.

Finally, I suggest you try to locate the condensing unit to a shady spot around your home if possible. Often I see the condensers sitting on the roof or baking on the West or South side of homes, which means they have to work that much harder to cool the home. Best to put them in the shade—North or East.

These ideas can help you stay cool, save money, and help the planet, all in one stroke.